Its not a con and it is real but this technique has some major downsides which is not being highlighted. You will notice that nothing moves in the video. Its a bit complicated to explain why that is but unless that is something that can be overcome then its always going to be a problem.

What this basically is, is a procedural 3D scene. Its exactly the same as my viewingdale but in 3D instead of 2D. Its a hierarchical array of objects with a fast traversal. As you zoom into an object it loads more layers of it. In the traditional way it would be polygons scaled up in vector but this technique is voxel based so that you can load in more and more layers of an octtree structure just like I would load in more and more smaller and smaller layers of quads in my map. In the same sense that if I change one icon at one scale level then it changes all the icons in the whole map since they are being reused. This is a problem for this scene generator since it means that you cant have local changes to one tree in that scene without affect them all or you have to store a cache of individual tree adjustments. That cache would be large and cumbersome for a detailed scene such as those shown because of the many layers of potential detail that you would need to store for each one. So when I see lots of animated stuff going on in a scene with that infinite detail I'll know its worth looking at.

Theres some discussion about it on the Outerra boards too since he is doing a 3D world terrain generator and has a similar requirement. But he is not doing it the same way but by using wavelets. You should look at his vids as well as they are mighty impressive esp when you zoom right down to centimeter scale and its still got detail in the ground terrain. YouTube some outerra vids. In a sense tho, even with his way there are still problems with animation since you need to know all of the wavelets before you start rendering. Its taking several hours to compute those but once you have them its fast to render. Another similar rendering style is radiosity where you can pre compute all the radiation levels in a scene which take ages and then render it from any view fast. Move something tho and all the radiation factors have to be redone once more.